A new self calibrating radiation planar microsensor. Application to contactless temperature measurement

Compared to conventional radiometers, this new microsensor, realized with thin film technologies presents a different location of the hot and cold junctions as well as symmetrical structure of the latter. Hot junctions are achieved by way of an infrared absorbing layer whereas the cold ones are coated with a thin golden reflecting film. The structure is designed so as to allow the microsensor to be manufactured onto a plane substrate with no need of etching cavities as for classical thermopiles. The latter often consists of a small number of thermocouples with enhanced thermal resistances while this new sensor trades this feature against numerous thermocouples fitted with very low internal thermal resistances. This microradiometer is therefore largely immune against convection mechanisms and remains operative in most circumstances without any encapsulation attachment. These overriding characteristics allow a direct control of the microsensor temperature by an independent heating for calibration or measurement purposes. Thus the device includes a planar thermocouple directed to measuring the average temperature of the sensor. The specific structure of this microradiometer enables a calibration-free and contactless temperature measurement which are original features of prime importance. The main purpose of this study is the realization or a contactless microthermometer allowing the effect of emissivity variations to be screened out. This device will prove to be instrumental in numerous industrial applications